The present invention concerns nitrogenous copolymers particularly useful as additives for improving the pour point properties of hydrocarbon middle distillates. It also concerns compositions of hydrocarbon middle distillates (fuel oils and gas-oils) containing such copolymers.
These copolymers are generally obtained by copolymerizing, by a radical process, monomers generating recurrent units (A), (B), (C) and (D). The compound generating recurrent unit (B) is preferably an anhydride of unsaturated dicarboxylic acid and the obtained copolymer is then reacted with a compound having a primary amine group, to convert at least partly the anhydride groups to imide groups.
The oil distillates concerned by the invention consist of middle distillates (fuel oils and gas-oils) having a distillation range (standard ASTM D86-87) from 150.degree. to 450.degree. C. and more particularly of gas-oils having a distillation range from an initial temperature of about 160.degree.-190.degree. C. to a final temperature of about 360.degree.-430.degree. C.
Many products of the market are recommended for improving the pour point of oil cuts of high paraffin content, such as for example:
polymers, essentially of long-chain olefins,
ethylene-vinyl acetate copolymers,
N-acylaminoethylesters of acid-containing polymers, or halogenohydrocarbon compounds.
On the other hand, U.S. Pat. No. 4,359,325 discloses terpolymers of average molecular weight from 500 to 250,000, formed of 10-94% by mole of units deriving from acrylic or methacrylic esters, 3-65% by mole of units deriving from dicarboxylic compounds (anhydride, diacid, amide, ester or N-substituted imide) and 3-40% by mole of units deriving from diisobutylene. The dicarboxylic units may have been modified, more particularly by condensation of such compounds as dimethylaminopropylamine, triethylenetetramine, tetraethylenepentamine, 2-aminopyridine, N,N-diethylethanolamine, diethanolamine, 1-cyanoguanidine, trimethylolpropane, glycerol and pentaerythritol. These terpolymers, when added to various hydrocarbon oils, for example in a proportion from 0.005 to 2% by weight, improve the pour point thereof.
European patent application 100,248 discloses additives particularly useful for lowering the cloud point of hydrocarbon middle distillates, defined as being polymers of average number molecular weight from about 1,000 to 10,000 obtained by condensation of one or more compounds having a primary amine group with a copolymer comprising:
(A) recurrent units originating from at least one linear alpha olefin,
(B) recurrent units deriving from at least one unsaturated .alpha.,.beta. dicarboxylic compound, in the form of a diacid, a lower alkyl diester or an anhydride, and
(C) recurrent units originating from at least one alkyl ester of unsaturated monocarboxylic acid.
The use of the additives disclosed in this patent application also results in a moderate decrease of the pour point of the middle distillates.
French patent application 2,528,667 discloses additives used for modifying the properties of middle distillates, particularly for lowering the cloud point of said distillates and, to a slight extent, their pour point.
These additives are disclosed as being the condensation products of at least one compound containing one primary amine group, particularly linear primary aliphatic monoamines of 12 to 24 carbon atoms, polyamines comprising a linear alkyl radical of 12-24 carbon atoms, ether-amines whose ether group comprises a linear alkyl radical of 12-24 carbon atoms or a primary, .alpha.,.omega. amino-alcohol of 10-18 carbon atoms, with a copolymer comprising:
(A) recurrent units originating from at least one alkyl ester of unsaturated monocarboxylic acid and/or at least one vinyl ester of saturated monocarboxylic acid,
(B) recurrent units originating from diisobutylene,
(C) recurrent units originating from at least one unsaturated .alpha.,.beta. dicarboxylic compound in the form of a diacid, a lower alkyl diester or an anhydride.
European patent application 112 195 discloses additives for middle distillates having the essential effect of decreasing the temperature at which the first paraffin crystals appear. These additives have also a small effect on the pour point of the middle distillates. They are described as products of number average molecular weight ranging from 1000 to 10,000 obtained by reaction of a compound having a primary amine group with a copolymer containing 20-40% by mole of recurrent units (A) originating from at least one linear alpha olefin, 30-70% by mole of recurrent units (B) originating from at least one unsaturated .alpha.,.beta. dicarboxylic compound in the form of a diacid, a lower alkyl diester or an anhydride, 5-30% by mole of recurrent units (C) originating from at least one alkyl ester of unsaturated monocarboxylic acid, and 5-15% by mole of recurrent units (D) originating from styrene and/or from at least one of its alkyl, halogen or methoxy derivatives.